1. Field of the Invention
The present invention relates to a method and apparatus for image compression in block units, particularly to the image editor, color equalizer and error diffuser functions thereof.
2. Description of the Related Art
One known method and apparatus for image compression in block units is disclosed in U.S. Pat. No. 5,956,431.
Normally, image data is called direct color, with each pixel holding color information. However, according to the above-referenced known image compression method, each pixel holds reference information relating to two representative colors and two interpolated colors (two bits each) instead of the color information. Processing is done in blocks of 4×4 pixels (hereinafter referred to as a “block”). This processing is characteristic in that only four colors are used in each block. These four colors are the two representative colors (16 bits) and the two colors gained through linear interpolation of these two representative colors. By allocating the color information in this way, the data volume can be reduced. Normally, information of 24 bits for 16 colors are required, but in this case, only 16-bit information for two colors are necessary. Each pixel holds only reference information showing which of the four colors should be used. The reference information is generated by an encoder during image compression.